Match patterns

Match patterns are a way to specify groups of URLs: a match pattern matches a specific set of URLs. They are for extensions using WebExtensions APIs in a few places, most notably to specify which documents to load content scripts into, and to specify which URLs to add webRequest listeners to.

APIs that use match patterns usually accept a list of match patterns, and will perform the appropriate action if the URL matches any of the patterns. See, for example, the content_scripts key in manifest.json.

Match pattern structure

All match patterns are specified as strings. Apart from the special "<all_urls>" pattern, match patterns consist of three parts: scheme, host, and path. The scheme and host are separated by "://".

<scheme>://<host><path>

scheme

The scheme component may take one of two forms:

Form

Matches

"*"

Only "http" and "https".

One of "http", "https", "file", "ftp", "app".

Only the given scheme.

host

The host component may take one of three forms:

Form

Matches

"*"

Any host.

"*." followed by part of the hostname.

The given host and any of its subdomains.

A complete hostname, without wildcards.

Only the given host.

host is optional only if the scheme is "file".

Note that the wildcard may only appear at the start.

path

The path component must begin with a "/".

After that, it may subsequently contain any combination of the "*" wildcard and any of the characters that are allowed in URL paths. Unlike host, the path component may contain the "*" wildcard in the middle or at the end, and the "*" wildcard may appear more than once.

<all_urls>

The special value "<all_urls>" matches all URLs under any of the supported schemes: that is, "http", "https", "file", "ftp", "app".

Examples

Pattern

Example matches

Example non-matches

<all_urls>

Match all URLs.

http://example.org/

ftp://files.somewhere.org/

https://a.org/some/path/

resource://a/b/c/
(unsupported scheme)

*://*.mozilla.org/*

Match all HTTP and HTTPS URLs that are hosted at "mozilla.org" or one of its subdomains.

http://mozilla.org/

https://mozilla.org/

http://a.mozilla.org/

http://a.b.mozilla.org/

https://b.mozilla.org/path/

ftp://mozilla.org/
(unmatched scheme)

http://mozilla.com/
(unmatched host)

http://firefox.org/
(unmatched host)

*://mozilla.org/

Match all HTTP and HTTPS URLs that are hosted at exactly "mozilla.org/".

Testing match patterns

When writing extensions, you don't generally work with match patterns directly: usually you pass a match pattern string into an API, and the API constructs a match pattern and uses it to test URLs. However, if you're trying to work out which match pattern to use, or debugging a problem with one, it can be useful to be able to create and test match patterns directly. This section explains how to do this.

Note that the code here will not work in an extension, and is only provided to help manually test match patterns using the console.

This gives you a command line that you can use to execute privileged JavaScript in Firefox.

Because code running in the Browser Console has system privileges, any time you use it to run code, you need to understand exactly what the code is doing. That includes the code samples in this article.

imports "MatchPattern.jsm": this is the system module that implements match patterns. Specifically, the module contains a constructor for MatchPattern objects. MatchPattern objects define a function called matches(), that takes a URI and returns true or false.

imports "BrowserUtils.jsm": this includes a function makeURI(), that converts a string into an nsIURI object. nsIURI is the type that matches() expects to receive.

Now you can construct MatchPattern objects, construct URIs, and check whether the URIs match: